For a number of years, manufacturers have attempted to produce plastic articles, such as vinyl siding, with simulated wood-grain or multicolored appearance. Various methods of forming such plastic articles have been used, but none has succeeded in achieving a realistic wood-grain appearance in which the wood-grain is strongly accented against the background. One known process for forming vinyl siding having some wood-grain appearance is shown in U.S. Pat. No. 4,048,101, to Nakamachi. The disclosure of U.S. Pat. No. 4,048,101 is hereby incorporated by reference. Nakamachi discloses a process for producing a synthetic plastic wood product with a multi-color appearance by forming colored particles of a first styrene resin with additives including a foaming agent, a foaming control agent, an inert inorganic foam nucleating material, and a dry colorant, and blending these colored particles with colored pellets of a second styrene resin having a lower melt flow index than the first resin. Nakamachi's blended resins are then coextruded at which time the foaming agent increases the volume of the blended resins by 10% to 300%, and produces an annular ring pattern. U.S. Pat. No. 5,387,781, to Saloom (the "Saloom patent") also discloses a method for imparting a wood-grain appearance by coextrusion of a capstock including accent color pellets consisting essentially of acrylics and/or polycarbonates with a polyvinylchloride ("PVC") substrate. The disclosure of U.S. Pat. No. 5,387,781 is hereby incorporated by reference. Saloom's lone example and only disclosed high deflection or softening point temperature acrylic resin, KMAX T-260, is no longer commercially available due to environmental concerns of its manufacturer. No polycarbonates and no other known mixture of acrylics has been found to yield even the marginal wood-grain effect achieved by KMAX T-260. Moreover, the method disclosed in Saloom results in somewhat unpredictable results because of the difficulty in simultaneously controlling the melt flow index and deflection or softening point temperature of KMAX T-260. KMAX T-260 is a resin having a high deflection or vicat softening point temperature, and a low melt flow index. The Saloom method does not result in bold, contrasting or "hard" streaking. Thus, there remains a need in the industry for a method of making simulated wood-grain plastic siding that gives predictable, controllable results in a pre-selected array of colors and boldness of streaking, in which the siding panels display a realistic wood-grain appearance, strongly accented against the background.